It is known to provide floor-type industrial vehicles, especially forklift trucks, with internal-combustion engines which generate the motive force and with hydrostatic transmissions connected between such engines and the drivable wheels of the vehicle. The internal-combustion engine can be an in-line engine, i.e., an engine in which a plurality of cylinders are disposed in a common plane, i.e., in line one behind the other parallel to the axis of the engine and especially the axis of its crankshaft upon which the pistons of these cylinders act.
A hydrostatic transmission for this purpose generally includes an axial piston pump whose input shaft is connected to the crankshaft and one or more hydrostatic (axial-piston) motors which are connected to the pump by hydraulic passages. The motors and/or the piston are of the variable displacement type to change the transmission ratio.
Such drive systems are provided for forklift trucks and, in general, industrial stackers which are generally driven at low speed and carry large loads.
Conventional vehicle systems using hydrostatic transmissions of the aforedescribed type generally provide the pump of the hydrostatic transmission along the line of the crankshaft, i.e., with a direct coupling between the pump shaft and the crankshaft. The pump is either directly flanged onto the internal combustion engine or is affixed to an intermediate housing and is driven by an intermediate shaft which, in turn, is driven by the crankshaft, the intermediate housing being mounted upon the cylinder block of the engine.
The hydrostatic pump may be separated from the hydrostatic motors or motor of the transmission and can be connected thereto by hydraulic lines. It is also known, however, to mount the pump and one or more motors in a common housing which also is oriented in line with the crankshaft of the engine.
This orientation is usually also maintained when the prime mover of the vehicle is an electric motor and, for the most part, the compact construction of the transmission is employed when the vehicle is driven by an electric motor. On the other hand, when the vehicle is driven by an internal-combustion engine, the hydrostatic transmission is of the separated type, i.e., the motor or motors are spaced from the pump and are connected thereto by hydraulic conduits.
For example, in the forklift truck described in U.S. Pat. No. 3,208,222, the hydrostatic pump is formed as part of a compact transmission of the type HW-10 and is connected via an intermediate shaft with the electric motor and is oriented coaxially to the latter.
A similar arrangement is used with this type of hydrostatic transmission in forklift trucks driven by internal-combustion engines and made by the same company. The internal-combustion engine is generally an in-line Boxer engine with recumbent cylinders, i.e., the plane of the axes of the engine cylinders being inclined to the vertical or practically horizontal.
In diesel transport vehicles of the Linde hydrotype, the crankshaft of the internal-combustion engine is connected via an intermediate shaft with the pump of the hydrostatic transmission which can either be of the compact type with two hydrostatic motors or in the separable type depending upon the particular vehicle construction.
In Linde forklift trucks of the type H-12 and H-40, the pumps of the hydrostatic transmissions driving the vehicle are disposed coaxial to the shafts of the internal-combustion engines and are directly flanged on the latter. These pumps are connected by conduits to the hydrostatic motors which are flanged to or built into the axles of the driving wheels of the vehicle. In the Linde forklift truck of type H-20, the pump is formed as part of a compact transmission and disposed along the axle. The transmission is connected via an intermediate housing to the cylinder block of the internal-combustion engine with the pump shaft coaxial to the crankshaft of this engine. As a consequence, a compact drive block is formed between the axle and the internal-combustion engine.
In the Linde forklift trucks of types H-50 and H-35 NG, the pump in each case is directly flanged to the internal-combustion engine and is constituted as an extension thereof. The pumps are here also connected by conduits with the hydrostatic motors disposed in the respective axles and connected in parallel to one another.
All of these arrangements have the disadvantage that the drive assembly, including the engine and the transmissions, have relatively large axial dimensions, i.e., dimensions parallel to the crankshaft of the internal-combustion engine.
Since certain vehicles, especially forklift trucks, must be used in tight locations and thus should be as short as possible, i.e., should have minimum axial length or length parallel to the direction of travel, this construction of the drive train has been found to be disadvantageous.